Discrete element modeling and fibre optical measurements for fluidized bed spray granulation

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Link, J.M. and Godlieb, W. and Deen, N.G. and Heinrich, S. and Tripp, P. and Peglow, M. and Kuipers, J.A.M. and Schönherr, M. and Mörl, L. (2006) Discrete element modeling and fibre optical measurements for fluidized bed spray granulation. In: 15th International Drying Symposium (IDS 2006), 20-23 August 2006, Budapest.

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Abstract:Spout fluidized beds are frequently used for the production of granules or
particles through granulation. The products find application in a large variety of
applications, for example detergents, fertilizers, pharmaceuticals and food. Spout fluidized
beds have a number of advantageous properties, such as a high mobility of the particles,
which prevents undesired agglomeration and yields excellent heat transfer properties. The
particle growth mechanism in a spout fluidized bed as function of particle-droplet
interaction has a profound influence on the particle morphology and thus on the product
quality. Nevertheless, little is known about the details of the granulation process. This is
mainly due to the fact that the granulation process is not visually accessible. In this work
we use fundamental, deterministic models to enable the detailed investigation of
granulation behaviour in a spout fluidized bed. A discrete element model is used
describing the dynamics of the continuous gas-phase and the discrete droplets and
particles. For each element momentum balances are solved. The momentum transfer
among each of the three phases is described in detail at the level of individual elements.
The results from the discrete element model simulations are compared with local
measurements of particle volume fractions as well as particle velocities by using a novel
fibre optical probe in a fluidized bed of 400 mm I.D. Simulations and experiments were
carried out for two different cases using Geldart B type aluminium oxide particles: a
freely bubbling fluidized bed and a spout fluidized bed with the presence of droplets. It is
demonstrated how the discrete element model can be used to obtain information about the
interaction of the discrete phases, i.e. the growth zone in a spout fluidized bed. Eventually
this kind of information can be used to obtain closure information required in more coarse
grained models
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Link to this item:http://purl.utwente.nl/publications/69257
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